Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for transmitting a unicast request indication in a wireless communication system.
Related Art
Universal mobile telecommunications system (UMTS) is a 3rd generation (3G) asynchronous mobile communication system operating in wideband code division multiple access (WCDMA) based on European systems, global system for mobile communications (GSM) and general packet radio services (GPRS). A long-term evolution (LTE) of UMTS is under discussion by the 3rd generation partnership project (3GPP) that standardized UMTS.
The 3GPP LTE is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.
Public safety networks provide communications for services like police, fire and ambulance. In this realm the requirement has been to develop systems that are highly robust and can address the specific communication needs of emergency services. This has fostered public safety standards that provide for a set of features that were not previously supported in commercial cellular systems. These standards have also been applied to commercial critical communications needs such as airport operations.
Two main areas of 3GPP LTE enhancement have been discussed to address public safety applications. First area is proximity services (ProSe) that identify mobiles in physical proximity and enable optimized communications between them. Second area is group call system enablers that support the fundamental requirement for efficient and dynamic group communications operations such as one-to-many calling and dispatcher working.
The 3GPP LTE can provide a multimedia broadcast multicast service (MBMS) service. The MBMS is a service which simultaneously transmits data packets to multiple users. If a specific level of users exists in the same cell, the respective users can be allowed to share necessary resources so that the plurality of users can receive the same multimedia data, thereby increasing resource efficiency. In addition, a multimedia service can be used with a low cost from the perspective of users.
One of the objectives of group communication is to evaluate ability of enhanced MBMS (E-MBMS) or other mechanisms to provide group communication for public safety applications. That is, it has been discussed that group communication for public safety applications may be provided via the E-MBMS or other mechanism. However, a service continuity problem may occur during outbound mobility from a multicast-broadcast single-frequency network (MBSFN) area to a non-MBSFN area. Accordingly, a method for solving the problem described above may be required.